1. Field of the Invention
The present invention relates to a sheet discharging apparatus wherein a sheet conveyed thereto is received by a pair of rotating blades thereof and then conveyed downwards.
2. Description of the Related Art
In Japanese Patent Application No. 6-101236, the present applicant proposed an invention relating to a sheet discharging apparatus for a printing machine. This invention has been made public in Japanese Patent Publication No. 7-309496. This invention will be explained referring to FIGS. 4 to 10.
As illustrated in FIG. 4, an outlet 300a of a printing machine 300 is connected to an inlet of a sheet discharging apparatus 101 through a sheet conveying apparatus 100. The sheet conveying apparatus 100 has plural endless belts driven by a conveying motor. A post card as a sheet is printed by the printing machine 300, and conveyed by the sheet conveying apparatus 100, and then received in the sheet discharging apparatus 101. Ink on the post card as received is dried while the card is supported and conveyed in the sheet discharging apparatus 101. Then, the post card is dropped onto a tray 116 situated in a lower part of the sheet discharging apparatus 101, and stored therein.
As illustrated in FIG. 5, the sheet conveying apparatus 100 includes a conveying surface 102 for guiding a sheet and a belt 105 for conveying the sheet along the conveying surface 102.
As illustrated in FIG. 5, the sheet discharging apparatus 101 has, as a main body, a frame 110 approximately in a form of a box. On an upper portion of the frame 110, two shafts 111 are situated along two side edges of the sheet to be conveyed, respectively. Each shaft 111 has a rotating blade 112 including four plates.
As illustrated in FIG. 6, the two shafts are situated parallel with each other and rotated inwardly in directions opposite to each other. Namely, the left shaft rotates clockwise, and the right shaft rotates anticlockwise, as seen in a vertical plane perpendicular to the shaft 111. The two rotating blades 112 fitted on the respective shafts coincide with each other in rotational phases thereof. Namely, positions of respective plates of one rotating blade coincide with those of the other rotating blade in the rotational direction.
As illustrated in FIG. 5, in the frame 110, a pair of upper and lower driving axes 113 is situated below each of the shafts 111. The driving axes 113, 113 of the same pair are connected by two belts 114. Each of the belts 114 has many receiving flaps 115 formed at a predetermined distance therebetween.
A discharging tray 116 is drawably situated at the bottom of the frame 110.
The sheet, after being printed thereon by the printing machine 300, is discharged to the outside of the machine. The printed sheet discharged from the printing machine 300 is placed on the conveying surface 102 of the sheet conveying apparatus 100. The belt 105 moves along the conveying surface 102. The sheet is supported at both side edges thereof by the pair of the rotating blades 112. Upon rotation of the shaft 111, the sheet is downwardly conveyed and held by the receiving flaps 115 therebetween. Moving belts 114 convey the sheet downwardly. Ink printed on the sheet is dried during conveyance, and then the sheet is dropped onto the discharging tray 116 to be stacked thereon.
In using the sheet discharging apparatus, inconvenience such that the printing sheet comes out of the belts 114 or plural sheets are supported on one receiving flap 115 may be caused. In this case, the printing sheet must be taken out from between the belts 114, 114 by a hand inserted between the two rotating blades 112, 112. The rotating blade 112 is freed from rotation of the shaft 111 when being touched by the hand and not driven by the shaft 111. Thus, safety in such manual operation is ensured even when the shaft 111 is rotating. Namely, the rotating blades 112 may not bite hands of an operator in such operation.
That is, in the sheet discharging apparatus 101, the rotating blade 112 and the shaft 111 are not completely connected with each other, therefore the rotating blade 112 can rotate freely relative to the shaft 111 when being affected by force. Namely, as illustrated in FIGS. 7 and 8, the rotating blade 112 includes an axis portion 120 rotatably fitted on the shaft 111 and four plates attached to an outer circumferential surface of the axis portion 120. The four plates are arranged to be spaced apart by an angle of 45.degree.. A coil spring 130 is fitted on the shaft 111 on a rear side of the rotating blade 112. A stopper 131 is fitted on the shaft 111 on a rear side of the coil spring 130. An engaging member 132, a pin, is attached to the shaft 111 on a forward side of the rotating blade 112. Engaging holes 135 are formed on a front-end portion of the rotating blade 112. The form of the engaging hole coincides with that of the engaging member 132. The coil spring 130 presses the rotating blade 112, thereby forcing the engaging holes 135 to be engaged with the engaging members 132. Thus, the shaft 111 and the rotating blade 112 are joined to rotate together.
When the rotating blade 112 is pressed in a direction opposite to the pressing direction of the coil spring 130, the coil spring 130 is compressed, thereby allowing the rotating blade 112 to come out of the engaging members 132. When the pressing force disappears, the rotating blade 112 is pressed by the coil spring 130 to come into contact with the engaging members 132, again. Thus, the rotating blade 112 and the shaft 111 come to rotate together.
As previously mentioned, in the sheet discharging apparatus 101, the rotating blade 112 and the shaft 111 are not completely connected with each other. The rotating blade 112 gets detached from the shaft 111 when being pressed in the direction for compressing the coil spring 130, thereby being freed from rotation of the shaft 111. And, when the outer force disappears, the rotating blade 112 is pressed by the coil spring 130 to again contact the engaging members 132, thereby interlocking the shaft 111. However, unless the engaging members 132 engage the engaging holes 135, a rotational phase between the shaft 111 and the rotating blade 112 is not set at a predetermined constant state. Consequently, after the operation as mentioned before for removing the printing sheet, phases of the respective two rotating blades 112, 112, i.e. positions of the plates 121 of each rotating blade in the rotational direction, may be displaced relative to each other.
Suppose a printing sheet 200 is supplied onto the two rotating blades 112, 112 whose phases are displaced relative to each other by an angle of 15.degree. as illustrated in FIG. 9. In the drawing, the left rotating blade 112L is set at a predetermined proper phase for receiving the printing sheet 200 to be processed, and a phase of the right rotating blade 112R is displaced by an angle of 15.degree.. As illustrated in FIG. 10, if the printing sheet 200 is supplied towards the rotating blades 112L, 112R, it collides with the plate 121 of the rotating blade 112R in the displaced phase. The rotating blade 112R fails to regularly receive the printing sheet 200, or fails to convey the sheet to the belt 114. In this way, sheet jamming occurs while conveying the sheet.
An object of the present invention is, in a sheet discharging machine having a pair of rotating blades detachably connected to respective rotating shafts, to allow phases of the two rotating blades to always coincide with each other.